Since you already have an EH-2, more difficult to find, the others are easily available, cheap and very useful if you like to play clean.
A compressor without being a sustainer will fall short for the result I'm talking about.
Try to find a CS-3 made in Japan with the DBX chip, they sound slightly better, but any CS-3 will do the trick.
A NS-2 works by fadeing out the already "dying" note before the noise floor can be heard, and the sustainer part in the CS-3 works in opposite mode by amplifying the fading note to give the ilusion of sustain. That's why they work so nice together.
The NS-2 cuts the noise out so the CS-3 can amplify without any noise. Since the EH-2 had already enhanced the upper frequencies, the result will not be muddy. That's how the magic happens.
